On The Measurement Methods For Inertial Instruments And The Error Analysis Based On Precision Centrifuge

Precision centrifuge is an important inertial navigation test equipment which operates in high-overload condition, it can provide sufficient input specific forces for inertial instruments, and especially give rise to sufficient excitation for the high-order error model coefficients of inertial instruments, which lays a foundation for accurately calibrating error model coefficients of inertial instruments and makes contribution to improving the precision of inertial navigation system. But in the process of calibrating an inertial instrument on precision centrifuge, the centrifuge errors have effects on the calibration accuracy of error model coefficients, and these effects on the calibration accuracy of some high-order error model coefficients are often large, therefore, the impacts of centrifuge errors on calibration results should be considered in the study of calibration of inertial instruments using centrifuge.The source of this research subject is mainly based on JML-1boomed precision centrifuge which is developed by Space Control and Inertial Technology Research Center of Harbin Institute of Technology for “137Project”，whose specifications catch up with the advanced world levels. The calibration test for gyro accelerometer is carried out for the first time in demestic on the basis of the successful development of the centrifuge, which obtains the second-order coefficient and the cross quadratic term of gyro accelerometer successfully. The calibration methods of inertial instruments on this equipment are studied, and the main researches are on the calibrations of high-order error model coefficients of the gyro accelerometer, the quartz accelerometer (including3accelerometers in the IMU-Inertial Measurement Unit), the gyroscope with single-degree-of-freedom and etc. The impacts of the centrifuge errors on the calibration accuracy of error model coefficients are analyzed, which makes contributions to raising the accuracy of inertial navigation system. The main contents of this dissertation are shown as follows:The calibration of accelerometer on JML-I centrifuge was taken as the research object, and the errors of JML-I centrifuge was summarized. The opinion that the research on the general uncertainty of centrifuge is the process of analyzing and synthesizing the centrifuge error sources was suggested, based on which the internal and the external error sources that may affect input specific forces of tested instruments supplied by centrifuge were analyzed comprehensively.The impact of each error on the input acceleration of accelerometer was achieved respectively. Propagating these errors using homogeneous transformation, the real specific force along each axis under the influences of centrifuge errors was obtained, which lays the foundation for researching the test method in order to improve the calibration accuracy by compensating for the errors in real test.The calibration method of second-order error model coefficient of Gyro Accelerometer (GA) on JML-I centrifuge was studied and corresponding errors were analyzed. Based on certain type of GA test on centrifuge, the integrated error model of GA was attained according to the kinetic equation of GA, and then the error model was simplified in engineering sense, which derived the error models of GA in single-axis centrifuge test, double-axis centrifuge test, and error model of cross quadratic term used in real calibration containing centrifuge errors. Two working modes of the counter-rotating platform of JML-I centrifuge were applied to calibrate K2term of GA respectively, and the errors were compensated. Corresponding calibration results were acquired from repetitive test which satisfied the calibration accuracy, so the correctness of the calibration method was verified. Meanwhile, the calibration method of cross quadratic term’s coefficient of GA was discusssed. The formation mechanism of cross quadratic term was analyzed and the test plan was designed according to the characteristics of the error model containing the cross quadratic term of GA and the analyses of centrifuge errors’ impacts. The cross quadratic term was calibrated successfully by the method in real test and the validity of the method was proved by comparing the calibration accurary with the K2term and corresponding error analyses.The calibration method of quartz accelerometer on centrifuge was studied. Combining the derived error model of quartz accelerometer and the precise input specific force along each axis of accelerometer acquired through analysis of centrifuge errors, the calibration method of error model coefficients of both the single accelerometer and the three accelerometers in IMU were designed in consideration of centrifuge errors. The calibration results were obtained through simulation verifying the corretness of the calibration mehods and the size of impact on the calibration accuracy of every accelerometer’s high-order coefficient was calculated by giving tolerance towards each centrifuge error, which lays the foundation for improving the calibration accuracy through error compensation in real test.The calibration method of static error model’s coefficients of single-degree-of-freedom gyroscope was designed. The working mode of synchronous reversal revolution of counter-rotating platform with the main axis of centrifuge was adopted, the installation axis was introduced and installations of gyroscope were designed. Multi-position of installation axis and double-sphere-composite test plan were applied in the calibration in consideration of centrifuge errors, and the test steps for real calibration were listed in detail. All the error model coefficients were calibrated successfully through simulation, which proved the validity of the designed method and laid the foundation for future research on combinational calibration of IMU on centrifuge.